Subscriber Norma had a great question about having Rich Snippets on out of stock pages:
But what's the point of having out of stock pages with rich snippets? Is it just to get people to her site in general? (even though they'll land on an out of stock page? Seems like it would cause a bounce)
First, Google takes a lot of factors into account for their rankings. Many of them are about a specific page, but there are some that are domain-level factors.
Let's say this customer was selling antique jewelry.
By keeping out-of-stock product pages online, Google is going to crawl them and see references to "jewelry", "antique", "necklaces", etc on those pages. They'll also see links to different categories called "1910 Jewelry", "1920 Jewelry", etc.
With enough of them, Google will be able to form the opinion "this site is about antique jewelry" which can lead to better overall rankings and search listings.
The second benefit is what I recommended she change her process to...
She should mark the product as out-of-stock, but also a add a message to the product page saying something to the effect of:
"I'm sorry that this unique 1910s necklace has been sold. Since every item I sell is rare or one-of-a-kind, they can go fast. Here are a few similar items that are available..."
That combined with a few links and product photos will let her take the traffic and customers to those discontinued products and use them on products that are in stock. Which should increase her sales.
I think she's going to do it manually because it will take all of 5 minutes to write up each one. But you could very easily do this with an app or custom code in your theme.
It's basically the same thing as those related product apps you see, just that it's only shown when a product it out-of-stock (which is like 2 lines of liquid code to show/hide).
So back to Norma's question.
Yes, the customer would bounce if the product was out-of-stock but with a little bit of work the majority of them could be recaptured.
Heck, even asking for an email opt-in to "hear about new products when they arrive" should take advantage of that discontinued product page.
Catching the attention of your potential customers is one of the key steps with marketing. That's what makes Rich Snippets in the organic search results so valuable, they are more attractive to people than regular old search listings.
And they are easy to get if you use my app, JSON-LD for SEO.